1. Field of the Invention
The present invention relates to pick hole guards for manhole covers.
2. Description of Related Art
Manholes are commonly found in urban environments, and elsewhere, and are constructed to provide access to underground utility systems, such as telephone, electric, gas and sewage systems. Manholes are almost always provided with “manhole covers” to secure the manholes from unauthorized access and to protect pedestrians from injury. The manhole covers often weigh in excess of 50 kilograms (100 pounds) and rest on a ridge of a support ring at the entrance of the manhole, with the edges of the manhole cover being snugly fit near, or against, inner facing walls of the support ring. As such, “pick holes” are typically formed in the manhole covers through which hook devices can be inserted for use in lifting the manhole covers when authorized personnel need access to the manholes.
Unfortunately, an undesirable consequence of having the pick holes (which are typically about ¾ inch or more in diameter) is that they are often indiscreetly used to dispose of undesirable and dangerous waste products. One epidemic that has plagued some cities is that used hypodermic needles and other waste products are thrown into the pick holes by users of illegal substances. This presents health hazards and dangers for maintenance people who service underground utilities, not to mention an environmental hazard to the general public.
U.S. Pat. No. 5,230,583 to Johnson describes a “Method of sealing openings in manhole covers using a pick hole plug.” A plug is formed in a pick hole of a manhole cover using soft rubber, which is allowed to cure in the pick hole in order to seal it. In order to remove the plug, it must be driven through the pick hole, and then recovered. Disadvantages of this method include, without limitation, having to recover the plug in the manhole, or elsewhere, assuming it is not destroyed or lost after being driven through. Also, the process of forming the plug in the pick hole when the plug is lost or destroyed is inconvenient and time consuming.
U.S. Pat. No. 5,056,955 to Spiess et al., relates to a “quick release locking means for a cover” for a manhole. The disclosed invention includes a manhole cover with cross-shaped slots and fixing plates, and therefore requires a modified manhole cover that may need to be manufactured. Disadvantages to this design, include, without limitation, that in order to replace the numerous (e.g., hundreds of thousands, if not millions) existing manholes, expenses would be very high.
U.S. Pat. No. 5,909,991 to Manion et al., also relates to a plug for openings on manhole covers. The plug has a shaft formed with projections. The projections are inserted into an opening on a manhole cover and contact the inside walls of the openings to help secure the plug in place. Again, the plugs must be removed to access the openings by pulling the plugs out of the openings and may require a tool, such as a screw driver, as suggested in the patent. As will be appreciated by those skilled in the art, removal of plugs from openings can be tedious if tightly fit and can often damage plugs. Also, it is noted that failure to keep track of the plugs once removed could result in significant moneys wasted. These are just some of the disadvantages noted in the prior publications.